Synthesis, thermal behaviour and luminescence properties of rare earth-doped titania nanofibers

The presence of RE elements shifted toward higher values the anatase to rutile phase transition temperature (up to 900-1000 °C), with the simultaneous formation of the Ln2Ti2O7 phase (Ln = Eu, Er). The Raman spectroscopy analysis revealed the typical anatase phase vibrational modes at 500 °C and the rutile phase ones at 1000 °C, accordingly to the XRD phase evaluations. In the case of La-doped sample, luminescence spectra were comparable to those registered for undoped TiO2, suggesting that La3+ doping did not cause a new luminescent phenomenon, but affected the response range and intensity. The luminescence spectra of Eu- and Er-doped samples clearly testified the presence of lanthanide ions in the TiO2 host lattice, showing the characteristic transitions of Ln3+ ions. The emission spectra were characterised by inhomogeneously broadened bands, suggesting a relevant disorder around the Ln3+ sites, typical of Eu3+ and Er3+ doped systems.